11. Conservation of Mass,       Charge, and Energy   Previous PageNext Page

7. When we balance a chemical equation by making the number of each kind of atom the same on both sides, what conservation principle are we using?

8. When O2 is combined with carbon to form CO2, is the oxygen oxidised or reduced? When chlorine gas is combined with carbon to form CCl4, is the chlorine oxidised or reduced? When O2 and Cl2 are combined to form the gas CL2O, which diatomic gas is oxidised and which of them is reduced?

9. Write the oxidation numbers for all the atoms in the molecules H2O, CO2, CCl4, and Cl2O.

10. Strict application of the rules for calculating oxidation numbers,1as given in Chapter 6, would lead to what values for C and H in methane, CH4? Then why do we say, as we did in this chapter, that the oxidation numbers of these atoms are effectively zero in methane, in discussing the nature of combustions?

11. What are the oxidation numbers of the atoms in NaBr and ClBr? When these compounds are formed from pure elements, does an actual transfer of electrons occur from one atom to the other? Which atom receives the electron, if transfer occurs? Are both of these compounds ionic salts? If not, what do different oxidation numbers mean for atoms in the compound that is not a salt?

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